1. Field of the Invention
The invention relates to a drive apparatus and a motor vehicle equipped with the drive apparatus. More particularly, the invention relates to a drive apparatus that includes an internal combustion engine capable of operating with a high expansion ratio by reducing the effective compression ratio through advancement of the intake valve closing timing, and a control method of the drive apparatus, and a motor vehicle equipped with the apparatus and the method.
2. Description of the Related Art
A related-art drive apparatus of the aforementioned type has been proposed which includes a motor-generator directly coupled to a crankshaft of the engine, and which drives and controls the motor-generator so as to stop the crankshaft of the engine at a desired position when a condition for stopping the engine is met. Such a drive apparatus is disclosed in, for example, JP(A) 2001-30408. In this drive apparatus, the engine is stopped at a predetermined position of the crankshaft of the engine, so as to improve the startability of the engine at the next time of starting the engine.
In the above-described drive apparatus, however, no consideration is given to the stop position in a high-expansion ratio cycle engine that is capable of attaining a high expansion ratio by reducing the effective compression ratio through advancement of the timing of closing an intake valve. In the high-expansion ratio cycle engine, if the intake valve is closed at an intermediate point during the intake stroke, the intake gas undergoes expansion, and then is compressed. Therefore, depending on the stop position of the engine, there may occur an incident where when the engine stops, a negative pressure exists in a cylinder, so that air enters the cylinder space via clearances between the cylinder and the piston, and therefore when the engine is next started, the compression ratio in the initial compression stroke becomes rather high, thus leading to a cause for knocking or the like.